1. Field of the Invention
The present invention relates to gate valves and more particularly to a gate valve having a fluid passageway closing disc therein with an opening in the disc supporting a fluid passageway closing plug rotated about its axis each time the gate valve is closed.
2. Description of the Prior Art
Gate valves presently in use for controlling the flow of high pressure fluids containing abrasive materials, such as sand, or the like, are usually provided with ring-like seats or sealing members surrounding the flow passageway on opposite sides of a disc slot normal to the axis of the flow passage which slidably receives a generally U-shaped disc having an aperture therein movable into and out of registration with the flow passageway for permitting and interrupting flow therethrough. My patent No. 3,871,616 discloses a gate valve of this type in which the metallic disc supports a plug member formed from ceramic material sealingly mating with like material disc seals or seats with the disc being movable between open and closed positions by a manually operated control wheel axially moving a valve stem contained by the bonnet of the gate. The ceramic plug member is rotatable within the disc but is not provided with means for rotating it about its axis. Thus the plug member normally seats against the flow passageway seals in the same position each time the gate valve is closed which in time results in wear of mating parts by the action of abrasive material in the fluid stream being controlled rather than the wearing action being distributed over the circumferential edge portions of the plug and seals as may be accomplished by rotating the plug member.